A water boiler operated on gas, natural gas or diesel is often used in a school, hospital, hotel, office, factory, military camp or the like to provide water for drinking or washing. However, there is always a risk of incomplete combustion that leads to the production of lethal carbon monoxide. Instead, an electric water boiler can be used. There are problems such as a low heating rate and a high thermal loss that causes a problem to the environment.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in the prior art.